Your very best bet is to find a good qualified (APDT) behaviourist/trainer to help you, but here are some suggestions which might help.
I agree with walking them separately for a while. I have a rescue with dog to dog issues and she is a lot worse when I walk the two dogs together.
It sounds a little like they're running riot and not paying any attention to you. There is nothing wrong with keeping them on-lead for a while to get them out of the habit of bombing off and bullying and get them to calm down a little on walks.. Your nervousness may well be adding to the problem but it's not easy to stop that if you are expecting trouble.. if they are on lead and can't do it, then you won't be nervous and they can't pick up on something that isn't there!
I'd REALLY focus on recall and do it individually - if you don't use a whistle already get one and start training them to recall to that as dogs hear whistles more than they'll notice you yelling. Take some REALLY tasty treats with you (bits of roast chicken work in this house) and only let them off where you know you can get the attention back on you quickly and easily and reward like mad with a tasty treat. Make yourself more interesting - take a ball or play lots of games with them to keep them focused on you. If recall is a problem then you can buy a harness and longline (this is a 10-15m line that you leave permanently attached to the harness on walks and within reach of you - so the dogs can't go too far from you) the line can drag on the ground and if the dog ignores recall then jump on the line and bring him back in... every time you want him - don't let him ignore you.
Basically, you want to break the habit they are in and the only way to do that is stop them doing it and offer them an alternative interest.. the more times a dog does something the more likely he is to do it. This works with bad habits AND good so you can use it to your advantage - the more times you let them off and get a successful recall if they spot another dog, then the more likely they will be to do it in the future.
It's hard work and there is no easy fix but you can change how you do things and manage them better and in time they will improve!
Hope that helps
